Bound Spirit

Ethereal Chains (Recharge 5-6): Melee Weapon Attack: +4 to hit, reach 10 ft., one creature. Hit: 6 (1d8 + 2) force damage, and the target is grappled (escape DC 12). While grappled in this way, the target is restrained and must succeed on a DC 12 Constitution saving throw at the start of each of its turns or take 3 (1d6) necrotic damage.

Possession (1/Day): The Bound Spirit can attempt to possess a creature within 5 feet of it that is grappled by its Ethereal Chains. The target must succeed on a DC 13 Charisma saving throw or be possessed by the Bound Spirit; the Bound Spirit then disappears, and the target gains the Possessed condition. The possession lasts until the body drops to 0 hit points, the Bound Spirit ends it as a bonus action, or the Bound Spirit is forced out by an effect like the dispel evil and good spell. When the possession ends, the Bound Spirit reappears in an unoccupied space within 5 feet of the body. The possessed target is aware of the Bound Spirit's presence but cannot take actions or control its body.